Electrical stimulation may be used as a form of therapy for several medical conditions. A stimulation device is implanted into the body at a particular location that is convenient for implantation, and the stimulation device provides electrical stimulation signals. A conduction path is created for the electrical stimulation signals by the presence of an implantable medical lead that includes individual conductive filars that are connected to electrodes on a distal end. The electrodes are positioned at a target site within the body to deliver the stimulation signals.
The implantable medical leads are often made at a length that is less than the distance from the target site to the implantation site of the stimulation device. This may be done to allow the implantable medical leads to be more easily tunneled into position at the target site than would be the case if the lead was significantly longer. This allows for a two-stage implantation where a lead extension is also used, which provides protection for the implanted lead and allows the implanted lead to remain in place if the extension needs to be replaced. The lead extension is positioned between the stimulation device and the implantable lead, and a distal end of the lead extension is an extension connector that receives a proximal end of the implantable lead. The proximal end of the lead includes electrical contacts that establish electrical connection with connectors within the extension connector, while filars extend between the proximal contacts of the extension and the electrical connectors within the extension connector located on the distal end of the extension. Thus, conduction paths from the stimulation device to the electrodes of the implantable lead are achieved.
There are drawbacks to this configuration that utilizes an extension. The extension connector may constrain the tunneling to a single direction. Furthermore, the extension connector on the distal end of the extension requires a different manufacturing method than proximal end of the extension which increases the costs and complexities of manufacturing of the extension. Additionally, the geometry of the extension connector may lead to discomfort for the patient and/or erosion of tissue beneath the skin of the patient.